Variable phase contrast microscope



May 5, 1953 H. MARX 2,637,243

VARIABLE PHASE CONTRAST MICROSCOPE Filed April 26, 1949 INVENTOR HELMUTMARX ATTORNEY Patented May 5, 1953 -VARIABLE PHASE CONTRAST MICROSCOPEHeknut;;;'Marx,,.,fiiessem Genmanymassignor. to Ermtleit wWetz au man aI corporation of. Germany Application-April26;:19493Se1i3l No.89,652

. InGermany November 20; 1948 17...,Qlaims.

ea le ha e c n ra t n thoxi f r. procucmgeptical. images of11011;;111m1110uS objects. such microscopes, there may be provided an;optical I system comprising, nntheside; of; the :light. source, anannular diaphragm, or a diaphragm consistng; of a; plurality ofdisklike.apertures; said diaphase, plate, by means ZOfi the condenser-sand theobjective lenses. ..'I;he phase plate lies in the rear focal plane ofthe'objective, or a corresponding plane, the shape of said phase platebeing con- =e;gruent.:withthe image of the-diaphragm,- However, withsuch a; phase plate; which his .soar- ..:ranged.that.it imparts initslannular. portion a 1 ,phase displacementvtotherays-compared to therays passing through therest ofthe plate, only .one phase diflerencev iohtainable.

; .It is. also. known to-.,practice.the .phase contrast 4 amethodby theuse.otlspeciallyarranged po1ariz ing means. and such "arrangements aredisclosed, for instance, by Harold Osterberg-(Journalof the a sopticalSociety of Americawvolume 37, No. 9, pages 726 to;730, The:Rolanretmicroscope).

.1With the 1 latten arrangements, any :phase difference betweenO?and:360?.is-obtainable.

:. Itis an objectzof the present invention-topmvide an improved phaseplate arrangement making it possible to obtain anydesircd phase differ-T ence with a microscopepf thegeneralnature de- ,lmicroscQ e accordingjtdthis invention is. accomplished by thep rovision of at least twophase plates arranged in series -in-the optical axis, each pair of phaseplates thawing in the place of the a i hra m. im a c rcula n ifo layeror thickness, whereby one full rotation results in In case of an annulardiaphragm image, the thickness of the congruent surface on the phaseplate increases in a cuneiform manner.

1 54 Upon lrotation againstz-eaclpotherof: the. phase v; wplates thusconstruntedgtheregis obtainemauni- Liorm. ,variation in: the 7 thicknessthroughout the diaphragm image area on the phaseeplatesy cor-:responding in each .case. to aparticularsphase displacement.-Alhe:thickness-;'between :the; transi- .ti on; points of the individualplatesirom the largest to;the/smallestg-thickness is diiferent by n 360as compared torthegthiekness ofsthe remainin portionmandathere isthusproduced the 1 same-phase displacement,

r {Theadrawingashowsetwo {embodiments ofv the invention asfollowsz Fig.3-1. represents ;-a eschematicy aXia1;.-s ection through. theqopticalsystem ofrga phase; contrast .-.microseope;

F s- 2:sho vs twoaphase plates each'having-a set a ofdisk-likediaphragmfimage-areas;

; I Fig: 13:showsrtwo phase platesihaving annular cuneiform-;areas;;and

Fig; e illustrates; the :effect :oi the. phase plates of 3:;Wh8187th35plates havee-been rotated against each other byian-angle a. Ia.Referring,mora-particularly tQ;Fig., 1, there is .2 shown a.condenserldiaphragm t,- zthe congruent image of iwhioh is-iprojeeted bycondenser. 2::and sobjecti ve. A :uponthemhase plates 5aand 5b whichareprovided mthe n reargj-focab,plane :of ithe objective.

; -The;vslide or. mount 3 dawtewedr-through: eye- ;-piece 6. In theembodiment ofa Fig. thewtwo'phase plates mend-Share Di-Oitided byqway,ofexample, with-nae diske-likeiphasesarcas 112,811,- Sa; l llaiand gs-;I la, and "lb, QbQQhi-Jflbrfifldi I lb, respectively, it i beinunderstoodthatthecondenserzdiaphiiagm I is oongnuently: constrnctedaAsashownbysshading, the thickness nfavthe. :said :diskelike areas in-..creases ill-12L (GIQCkWllSBsdililififllillhl. onzip at ia dmfiGOunter-clockwise. one plate 52):, *each. successive pair increasingin thickness by substantially the same amount. These thicknesses may bevaried in accordance with the instrument used and the results desiredand the present invention is in no 45 way limited to specific thickness.

The phase plates shown in Fig. 3 are intended to be used in connectionwith a condenser diaphragm having an annular opening. The congruentlyformed thickened portions of the phase 5 plates have a cuneiformlyincreasing thickness (also indicated by shading), said thickness onplate 5a increasing clockwise from lZa to l3a, while it increasessimilarly but counter-clockwise on plate 51) from [21) (havingsubstantially the same thickness as l2a) to I31; (having substantiallythe same thickness as I3a) By disposing the phase plates of Figs. 2 or 3one after the other by rotating the said plates by a certain angle a(see Fig, 4) against each other, the total or combined thickness of thephase areas of the two phase plates will be the same at all pointsexcept the area between the two points of transition from maximum tominimum thickness, in which area the thickness differs from theremainder area by a value of n 360.

I claim:

1. In a phase microscope having a generally annular condenser diaphragmwhose image is projected by a condenser and an objective in an exitpupil of the objective: at least one pair of phase plates adjacent eachother and disposed in the exit pupil, a generally annular lightphasechanging layer increasing in thickness in clockwise direction onone of said plates, and a generally annular light phase-changing layerincreasing in thickness in counter-clockwise direction on the other ofsaid plates, the two phase plates being mounted for rotation relative toeach other. v

2. Phase plates as defined in claim 1, wherein the thickness of one ofsaid layers increases cunei formly in clockwise direction while thethickness of the other layer increases cuneiformly in counter-clockwisedirection.

3. In a phase microscope having a generally annular condenser diaphragm,a condenser, and

an objective with an exit pupil, an image of the diaphragm beingprojected in the exit pupil by means of the condenser and objective: atleast one pair of phase plates arranged adjacent each other in the rearfocal plane of the objective, a generally annular light phase changinglayer increasing in thickness in clockwise direction on one of saidplates, and a generally annular light phase changin layer increasing inthickness in counter-clockwise direction on the other of said plates,the two phase plates being mounted for rotation relative to each other.

4. In a phase microscope having a generally annular condenser diaphragmarranged concentrically with respect to the optical axis of themicroscope, the image of the diaphragm'being projected by a condenserand an objective in an exit pupil of the objective: at least one pair ofphase plates arranged adjacent each other in said optical axis anddisposed in the exit pupil, a light phase-changing layer congruent withthe diaphragm image projected thereon on each phase plate, the layer onone phase plate increasing in thickness in clockwisedirection, and thelayer on the other phase plate increasing in thickness incounter-clockwise direction, said plates being mounted for rotationrelative to each other so that after a complete rotation of one platerelative to the other there is produced a phase differ- 4 ence incrementof n x 360 (n being an integer of 1 or more).

5. In a. phase microscope having a condenser diaphragm of a plurality ofapertures arranged annularly around the optical axis of the microscope,theimage of the diaphragm being projected by a condenser and anobjective in an exit pupil of the objective: at least one pair of phaseplates arranged adjacent each other in said optical axis and disposed inthe exit pupil, a plurality of light phase-changing layers congruentwith the image of said diaphragm apertures projected thereon on eachphase plate, each more) 6. Phase plates as defined in claim -5, whereinsaid diaphragm apertures are circular and said congruent phase-changinglayers increase successively by a predetermined thickness, saidthickness being expressed by the formula (n being an integer of 1 ormore, and m being the number of apertures).

v7. In a phase microscope having a generally annular condenser diaphragmwhose image is projected by a condenser and an objective in an exitpupil of the objective: at least one pair of phase plates adjacent eachother and disposed in a plane corresponding to the rear focal plane ofthe objective, a generally annular light phasechanging layer increasingin thickness in clockwise direction on one of said plates, and agenerally annular light phase-changing layer increasing in thickness incounter-clockwise direction on the other of said plates, the two platesbeing mounted for rotation relative to each other.

HELMUT MARX.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,244,687 Goldsmith et al. June 10, 1941 2,427,689 Osterberget al. Sept. 23, 1947 FOREIGN PATENTS Number Country Date 636,168Germany Oct. 7, 1936

